Detection of pathogens in Dermacentor reticulatus in northwestern Europe: evaluation of a high-throughput array

Background: The geographic distribution of Dermacentor reticulatus is expanding in Europe. Surveillance of this tick species and its pathogens is desirable, as it transmits pathogens of public and veterinary importance. A high-throughput real-time PCR-based array was used to screen 1.741 D. reticulatus ticks from Belgium, Germany, The Netherlands, and Great Britain for the presence of 28 tick-borne bacteria and twelve protozoan parasites. The presence of pathogen DNA was confirmed by conventional PCR followed by sequencing. Results: The array detected the presence of DNA from Borrelia spp. (7%), B. afzelii (0.1%), B. garinii (0.1%), B. spielmanii (0.1%), B. miyamotoi (0.2%), Anaplasma marginale (0.1%), A. phagocytophilum (0.1%), Ehrlichia canis (2%), Rickettsia helvetica (0.2%), spotted fever group Rickettsia (9.6%), Francisella tularensis or Francisella-like endosymbionts (95%), Coxiella burnettii (0.1%), Babesia divergens (0.2%), B. canis (0.9%) B. vogeli (5.6%), and Theileria equi (0.1%). Only the presence of B. canis and spotted fever group Rickettsia could be confirmed by conventional PCR and sequencing. The spotted fever Rickettsia-positive samples were all identified as R. raoultii. Conclusions: We successfully detected and determined the prevalence of B. canis and R. raoultii in D. reticulatus. An high-throughput array that allows fast and comprehensive testing of tick-borne pathogens is advantageous for surveillance and future epidemiological studies. The importance of thorough validation of real-time PCR-based assays and careful interpretation is evident.